The present invention relates to hair care compositions which contain a hydrophobic cationic emulsion of a highly branched and crosslinked silicone polymer, preferably polydimethylsiloxane. These silicone emulsions can be formulated into conditioners, styling gels, pump sprays, permanent hair waving products, and the like and are especially effective in enhancing the wet and dry combing of hair.
It is well known in the art that the incorporation of polydimethylsiloxanes into hair care formulations enhances the manageability, appearance and feel of treated hair. For example, U.S. Pat. No. 4,243,657, issued Jan. 6, 1981, discloses a hair care composition including polydimethylsiloxanes and diol derivatives or branched aliphatic alcohols. Recently, aminoalkyl substituted polydiorganosiloxanes have become popular in hair care formulations. These aminoalkyl substituted polydiorganosiloxane polymers are typically dimethylsiloxane polymers in which some of the methyl groups attached to the polymer chain are replaced by organic groups of amine functionality. Such aminofunctional siloxanes show a stronger affinity for hair surfaces and are not removed as easily as other siloxane polymers. In addition, the aminofunctional siloxanes have been shown to have a greater effect in reducing the average combing force. U.S. Pat. No. 4,563,347, issued Jan. 7, 1986, and U.S. Pat. No. 4,749,732, issued June 7, 1988, teach the use of aminoalkyl substituted polydiorganosiloxanes with other components in hair care compositions to improve combing and feel characteristics. Great Britain Patent No. 2,058,103, (published Apr. 8, 1981), discloses hair conditioning compositions containing a cationic polymer and an oil in water emulsion of an aminofunctional polydimethylsiloxane which improves ease of combing.
In accordance with the present invention, however, it has been discovered that aminoalkyl groups are not necessary to improve the combing and feel characteristics of hair. Instead, the present inventors have found that it is possible to incorporate a hydrophobic cationic emulsion of a highly branched and crosslinked polydimethylsiloxane, hereinafter referred to as the silicone emulsion, into hair care formulations. The degree of crosslinking distinguishes the emulsion of this invention from other emulsions used in the field of cosmetics. For example, U.S. Pat. No. 4,696,969, issued Sept. 29, 1987, discloses an aqueous emulsion composition which can be employed in hair conditioners, which includes a linear polydimethylsiloxane base polymer fluid having a viscosity of up to 100,000 cps. Unlike the prior art, however, the present invention benefits from a crosslinked polydimethylsiloxane. Crosslinking occurs when polyfunctional compounds having more than two functional groups per molecule are used.
A toluene solubility test provides a simple method to distinguish between linear and nonlinear polydimethylsiloxanes because linear siloxanes are soluble in toluene whereas branched and crosslinked siloxanes are not. In addition to differences in solubility, linear and nonlinear polydimethylsiloxanes exhibit different physical properties. Linear polydimethylsiloxanes are liquids which exhibit viscous flow, even at high molecular weights. Branched or crosslinked polydimethylsiloxanes of comparable molecular weight are elastomers. Since the two classes of siloxane polymers have such significant differences in physical properties, it would not be obvious to substitute a highly branched and crosslinked siloxane for a predominantly linear siloxane in hair treatment compositions.
A hydrophobic cationic emulsion of a highly branched and crosslinked silicone polymer for use in fabric care applications to improve rewettability is described in U.S. Pat. No. 4,908,140, issued Mar. 13, 1990, and assigned to the same assignee as the present application. U.S. Pat. No. 4,908,140 discloses a method of enhancing the rewettability of fabrics treated in a laundering operation by contacting the fabrics with a mixture including a rinse cycle fabric softening conditioning composition and a hydrophobic cationic emulsion of a silicone polymer inorder to improve the water absorbing capabilities of fabrics.
However, use of the hydrophobic cationic emulsion in hair care formulations provides advantages neither taught nor appreciated by U.S. Pat. No. 4,908,140. For example, hair care products were not contemplated by U.S. Pat. No. 4,908,140 and hair treated in accordance with the present invention possesses improved wet and dry combing properties which is unrelated to enhancing water absorbency. The hydrophobic silicone emulsion of the present invention effectively sheets the surface of hair making the hair easier to comb and more desirable to feel. Accordingly, the present invention provides compositions and methods of hair treatment possessing significant advantages over the prior art.